Publications by authors named "Emily L Dennis"

Article Synopsis
  • A study found that changes in the brain entorhinal cortex (EC) and specific blood lipids are linked to Alzheimer's disease (AD) in individuals with the apolipoprotein E ε4 genetic variant.
  • Analysis of brain imaging and lipid profiles revealed that ε4 carriers with mild traumatic brain injury (mTBI) had thicker left ECs, but repeated mTBIs reduced right EC thickness.
  • The research highlights the need for further investigation into the relationship between ε4, mTBI, and specific blood lipid ratios as potential biomarkers for early detection of AD in affected individuals.
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Introduction: Neuroimaging has expanded our understanding of pediatric brain disorders in which white matter organization and connectivity are crucial to functioning. Paralleling the known pathobiology of many neurodevelopmental disorders, traumatic brain injury (TBI) in childhood can alter trajectories of brain development. Specifically, diffusion tensor imaging (DTI) studies in TBI have demonstrated white matter (WM) abnormalities that suggest microstructural disruptions that may underlie atypical neurodevelopment.

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Importance: Blast-related mild traumatic brain injuries (TBIs), the "signature injury" of post-9/11 conflicts, are associated with clinically relevant, long-term cognitive, psychological, and behavioral dysfunction and disability; however, the underlying neural mechanisms remain unclear.

Objective: To investigate associations between a history of remote blast-related mild TBI and regional brain volume in a sample of US veterans and active duty service members.

Design, Setting, And Participants: Prospective cohort study of US veterans and active duty service members from the Long-Term Impact of Military-Relevant Brain Injury Consortium-Chronic Effects of Neurotrauma Consortium (LIMBIC-CENC), which enrolled more than 1500 participants at 5 sites used in this analysis between 2014 and 2023.

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Article Synopsis
  • * It's important not just to detect brain changes but also to connect these changes to how well a child functions, thinks, and behaves after a TBI.
  • * Research shows that advanced neuroimaging can help predict outcomes after TBI and may offer new chances for interventions in pediatric cases.
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Article Synopsis
  • Neuroscience researchers are leveraging Big Data to improve the reliability of findings by increasing sample sizes and addressing replication issues.
  • A study analyzed data from 53 studies with over 10,500 participants to connect scores from various auditory verbal learning tasks (AVLTs) while controlling for site-related effects.
  • The research successfully reduced score variance by 37% and developed an online tool to help researchers and clinicians convert memory scores across different tests, highlighting the benefit of global data harmonization in behavioral sciences.
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Deficits in memory performance have been linked to a wide range of neurological and neuropsychiatric conditions. While many studies have assessed the memory impacts of individual conditions, this study considers a broader perspective by evaluating how memory recall is differentially associated with nine common neuropsychiatric conditions using data drawn from 55 international studies, aggregating 15,883 unique participants aged 15-90. The effects of dementia, mild cognitive impairment, Parkinson's disease, traumatic brain injury, stroke, depression, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, and bipolar disorder on immediate, short-, and long-delay verbal learning and memory (VLM) scores were estimated relative to matched healthy individuals.

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Objective: The long-term consequences of traumatic brain injury (TBI) on brain structure remain uncertain. Given evidence that a single significant brain injury event increases the risk of dementia, brain-age estimation could provide a novel and efficient indexing of the long-term consequences of TBI. Brain-age procedures use predictive modeling to calculate brain-age scores for an individual using structural magnetic resonance imaging (MRI) data.

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Background And Objectives: Traumatic brain injury (TBI) is a concern for US service members and veterans (SMV), leading to heterogeneous psychological and cognitive outcomes. We sought to identify neuropsychological profiles of mild TBI (mTBI) and posttraumatic stress disorder (PTSD) among the largest SMV sample to date.

Methods: We analyzed cross-sectional baseline data from SMV with prior combat deployments enrolled in the ongoing Long-term Impact of Military-relevant Brain Injury Consortium-Chronic Effects of Neurotrauma Consortium prospective longitudinal study.

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Background And Purpose: Sport-specific training may improve postural control, while repetitive head acceleration events (RHAEs) may compromise it. Understanding the neural mechanisms underlying postural control may contextualize changes due to training and RHAE. The goal of this study was to determine whether postural sway during the Balance Error Scoring System (BESS) is related to white matter organization (WMO) in collegiate athletes.

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Article Synopsis
  • Resting state functional magnetic resonance imaging (rsfMRI) is a valuable tool for studying brain connectivity, particularly in relation to neurological disorders like traumatic brain injury (TBI), but there is a lack of standardization in how it is used across different research groups.
  • This narrative review aims to tackle key methodological challenges in rsfMRI research for TBI by providing recommendations for data acquisition, processing, and analysis to enhance the reliability and comparability of study results.
  • The review consists of a literature search on current rsfMRI studies, a set of seven recommendations for improving research practices, and a discussion of future research directions to promote rigorous methods and transparency in the TBI research community.
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Article Synopsis
  • MRI is a key tool in researching diagnostic and prognostic markers after traumatic brain injury (TBI), particularly to understand mild TBI (mTBI), but findings are often inconsistent, highlighting the need for further study.
  • The study analyzed MRI data from 976 military veterans and service members to explore the links between imaging outcomes and clinical features of mTBI, using regression models to account for factors like age and sex.
  • Results indicated that while no major differences were found between those with and without mTBI history, blast-related mTBI showed significant brain volume reductions in certain areas, and multiple mTBIs correlated with specific MRI findings.
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  • The study explores the lesser-known role of the cerebellum in PTSD by analyzing cerebellar volume differences in a large sample of 4,215 adults, with 1,642 diagnosed with PTSD and 2,573 as healthy controls.
  • Using advanced deep-learning techniques, researchers assessed the total cerebellum volume and 28 subregions, revealing significant reductions in both gray and white matter in individuals with PTSD, especially in specific posterior lobe and vermis areas.
  • The results suggest that changes in cerebellar structure are linked to cognitive and emotional dysfunctions in PTSD, highlighting the cerebellum's importance beyond its traditional role in motor control.
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Article Synopsis
  • The study investigates the relationship between traumatic brain injury (TBI) and changes in brain connectivity, particularly in military personnel with different histories of TBI during combat versus non-combat situations.
  • It focuses on how functional connectivity (FC) in brain regions related to movement, like the basal ganglia, varies depending on the context of the injuries.
  • The results reveal that those with deployment-related mild TBI have increased connectivity in certain brain areas, while non-deployment mild TBI was linked to significant correlations with walking performance, suggesting different behavioral outcomes based on the circumstances of the injury.*
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Posttraumatic stress disorder (PTSD) is associated with lower cortical thickness (CT) in prefrontal, cingulate, and insular cortices in diverse trauma-affected samples. However, some studies have failed to detect differences between PTSD patients and healthy controls or reported that PTSD is associated with greater CT. Using data-driven dimensionality reduction, we sought to conduct a well-powered study to identify vulnerable networks without regard to neuroanatomic boundaries.

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Importance: Traumatic brain injury (TBI) is known to cause widespread neural disruption in the cerebrum. However, less is known about the association of TBI with cerebellar structure and how such changes may alter executive functioning.

Objective: To investigate alterations in subregional cerebellum volume and cerebral white matter microstructure after pediatric TBI and examine subsequent changes in executive function.

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Article Synopsis
  • * Researchers utilized various MRI data types to identify brain features that can distinguish PTSD from controls, revealing that classification accuracy decreases significantly when using multi-site data compared to single-site studies.
  • * The denoising variational autoencoder (DVAE) model showed improved generalization on new datasets, indicating its potential for better classification of PTSD, although overall performance still remained only slightly above chance levels.
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Mild traumatic brain injury (mTBI) is the most common form of brain injury. While most individuals recover from mTBI, roughly 20% experience persistent symptoms, potentially including reduced fine motor control. We investigate relationships between regional white matter organization and subcortical volumes associated with performance on the Grooved Pegboard (GPB) test in a large cohort of military Service Members and Veterans (SM&Vs) with and without a history of mTBI(s).

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Background And Objectives: Repeated impacts in high-contact sports such as American football can affect the brain's microstructure, which can be studied using diffusion MRI. Most imaging studies are cross-sectional, do not include low-contact players as controls, or lack advanced tract-specific microstructural metrics. We aimed to investigate longitudinal changes in high-contact collegiate athletes compared with low-contact controls using advanced diffusion MRI and automated fiber quantification.

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Treatment of youth concussion during the acute phase continues to evolve, and this has led to the emergence of guidelines to direct care. While symptoms after concussion typically resolve in 14-28 days, a portion (∼20%) of adolescents endorse persistent post-concussive symptoms (PPCS) beyond normal resolution. This report outlines a study implemented in response to the National Institute of Neurological Diseases and Stroke call for the development and initial clinical validation of objective biological measures to predict risk of PPCS in adolescents.

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Article Synopsis
  • This special issue focuses on various methods aimed at enhancing the harmonization of both existing and upcoming research data.
  • The implementation of these methods is anticipated to aid research across different clinical conditions, enabling more in-depth exploration of diverse questions.
  • By utilizing larger and more diverse samples, researchers can gain insights that were not possible with previous data sets.
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Neuroimaging technologies such as computed tomography (CT) and magnetic resonance imaging (MRI) have been widely adopted in the clinical diagnosis and management of traumatic brain injury (TBI), particularly at the more acute and severe levels of injury. Additionally, a number of advanced applications of MRI have been employed in TBI-related clinical research with great promise, and researchers have used these techniques to better understand underlying mechanisms, progression of secondary injury and tissue perturbation over time, and relation of focal and diffuse injury to later outcome. However, the acquisition and analysis time, the cost of these and other imaging modalities, and the need for specialized expertise have represented historical barriers in extending these tools in clinical practice.

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Article Synopsis
  • - This study explored the link between sleep health and cognitive control in the brain using fMRI data from 81 healthy adults, highlighting how sleep quality affects brain activity during cognitive tasks.
  • - Results showed that poorer sleep health correlated with heightened and widespread brain activation during reactive cognitive control, suggesting a "hyper-reactive" state in response to cognitive demands.
  • - Additionally, it was found that longer task engagement led to increased activation in those with poor sleep quality, while shorter sleep duration was tied to reduced brain activation and worse task performance, indicating potential inefficiencies in neural processing.
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Article Synopsis
  • Researchers in neuroscience are using Big Data to improve the reliability and replication of cognitive studies, focusing on memory testing.
  • They conducted a mega-analysis with data from 53 studies, involving over 10,500 individuals, employing methods to harmonize data and reduce variability across different sites.
  • Their findings show that large-scale data sharing can enhance the reproducibility of research in behavioral sciences, and they offer a free conversion tool for this purpose.
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Magnetic resonance spectroscopy is a powerful, non-invasive, quantitative imaging technique that allows for the measurement of brain metabolites that has demonstrated utility in diagnosing and characterizing a broad range of neurological diseases. Its impact, however, has been limited due to small sample sizes and methodological variability in addition to intrinsic limitations of the method itself such as its sensitivity to motion. The lack of standardization from a data acquisition and data processing perspective makes it difficult to pool multiple studies and/or conduct multisite studies that are necessary for supporting clinically relevant findings.

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